How to generate hmac-sha256 with sdk12.3.0 ?

[swetha Paladugu]

Hi,

I have a NRF51802 custom board, using sdk12.3.0 and softdevice 130 for my applications.

I would like to generate hmac sha 256 in my application. 

Can you please provide me an example to generate hmac?

In SDK 12.3.0 i couldn't find any example or development.

Please do the needful..

Thanks,

Swetha.

[Jørgen Holmefjord]

Hi,

The cryptographic library in SDK 12.3.0 is very limited, and only supports SHA256 Hashing algorithm, not HMAC, see Library usage. 

That being said, there is no HW cryptographic acceleration features on the nRF51 series, so any C embedded crypto library that can run on a ARM Cortex M0 CPU should be possible to integrate with your application.

Best regards,
Jørgen

[swetha Paladugu]

In opensource i got sha2.c and sha2.h files along with hmac.c and hmac.h files.

If i use the opensource library, is it necessary that i should sha256.c and sha256.h of nrf sdk 12.3.0 instead of sha2.c and sha2.h of opensource.. or can i use the open source sha2.c and sha2.h files directly?

What do u suggest?

Thanks,

Swetha.

[Jørgen Holmefjord]

Most likely it will be easier to use the sha2.c/h files from your opensource library, as the input structures for the function calls may be more aligned. The sha256.c/h files in the SDK also originates from an opensource repository, as mentioned in the header:

 *          This code is adapted from code by Brad Conte, retrieved from
 *          https://github.com/B-Con/crypto-algorithms.

[swetha Paladugu]

Ok i am using open source sha2.c/h files and i am able to generate hmac succesfully..

I am using this software hmac in my code for totp computations, i see that the computations are taking more time. Usually it happens with in a second.. Now i see that is taking more time.. 

Is it because we are doing everything in software, like this hmac?

Hardware crypto way of hmac generation would be faster right?

[Jørgen Holmefjord]

Yes, typically software takes longer time than hardware implementations. Also note that the Cortex M0 of nRF51 series ICs runs at 16 MHz, which will make the software operations 4 times slower than for instance nRF52 series running at 64 MHz.

[swetha Paladugu]

Thanks for your information Jorgen.